Contrastive analysis is basic to all linguistics since only by this approach can a general theory of language (language universals) be constructed and only with at least implicit contrastive analysis can a particular language be fully characterized. Two kinds of contrastive analysis have been basic to diachronic linguistics: the comparison of sister languages to discover the history of their divergence (comparative method) and the comparison of different stages of the same language to discover the history of change in the language. Diachronic contrastive analysis [comparing stages X1, X2...XN where X1 is zero and XN a full natural language] is basic to the study of child language development and promises benefits also to general theory and particular language characterization. (Author/JD)